col rob fredell, ph.d. military assistant to the chief scientist of the air force presented to afosr...
TRANSCRIPT
Col Rob Fredell, Ph.D.Military Assistant to the Chief Scientist of the Air Force
Presented to AFOSR Workshop on Prognosis
19 February 2008
A Paradigm Shift in Structural Life Prognosis
…recapturing USAF aircraft availability, performance and supportability
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
2
Overview
Aging aircraft in perspective
Carefree Structures
High-Velocity Maintenance
Prognosis Role as Integrator
Summary
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
3
Aging Aircraft in Perspective
“I don’t want to have to write a letter…Your son or daughter is dead because the wing fell off on takeoff. We knew it was going to fall off, we just didn’t know when.”
- General Ron Keys, COMACC, as quoted in USA Today, 8 May 2007
“The US Air Force has grounded its entire fleet of 676 F-15 fighter jets after a jet crashed on a training mission in Missouri last week.”
- BBC on-line, 6 November 2007
"It's kinda like taking your…1970 Chevrolet and tearing it down, repairing anything you find wrong with it--extending the life of the car.”
- Keith Gilstrap, Warner Robins ALC, as quoted in the Aim Points, 12 Feb 2008
“"We're trying to catch up with 20 years of neglect.”
- Loren Thompson, the Lexington Institute, in the Dayton Daily News, 11 Feb 2008
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
4
Top 10 Maintenance Drivers (MMH), Total AF
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
03 11 04 13 46 14 74 23 76 12
Mil
lio
ns
WUC
MM
H
20012002200320042005
WUC WUC Description% of Total FY05
MMH Hrs03 LOOK PH OF SCH INSP 14%11 AIRFRAME 12%04 SPECIAL INSPECTIONS 11%13 LANDING GEAR 8%46 FUEL SYSTEM 5%14 FLIGHT CONTROLS 5%74 FIE CONTROL 4%23 POWER PLANT 4%76 TAC ELEC WRFRE SYS 3%12 CKPT & FUSE COMPTS 3%
68%Total of Top 10 =
Finding, fixing cracks and corrosion: trending upward
Sch
edul
ed in
spec
tions
Air
fram
e re
pair
Spe
cial
insp
ectio
ns
Lan
ding
gea
r
Fue
l sys
tem
s
Ma
inte
nan
ce M
an
Ho
urs
(MM
H)
Prop
ulsi
on
Maintenance CategoryDISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Lack of investment in structures sustainment costing USAF…
..while continued investment in propulsion paying big dividends
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Missouri Air National Guard Mishap2 Nov 2007
• Aircraft broke up in flight
• Pilot ejected with injuries
• Forward fuselage separated from acft
Separation occurred here
Source: www.af.mil
• Cause: Fatigue of “fatigue proof” upper cockpit longeron from mfg defect
• 700+ aircraft grounded for detailed inspections
• 162 aircraft remain grounded as of 11 Feb 08
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Prognosis lesson learned: make sure you look in the right place!
6
Center Wing Box fatigue, corrosion limiting life of E, H fleets Many aircraft at or past upper limit for unrestricted use Warner Robins ALC executing 3-phase program to renew H CWB
3-year program to redesign wing splice fitting Sole source purchase of conventional replacement CWBs and production data Competitive purchase of 100s more replacement CWBs Heavier Extended Service Life (ESL) wing for all new J models?
J models currently produced with similar wing as E, H replacements More powerful engines, higher TOGW Higher usage and severity factors mean similar cracking problems in ~20 years ESL wing costs 1,000 lbs of added structure; reduces aircraft performance
Impact on availability Reduced availability and increased support costs Affects hundreds of aircraft supporting Air Mobility Command, AF Special
Operations, US Coast Guard, US Navy, and many foreign partners
C-130 Structural Health Assessment
7
SecAF charge: break this cycle
SecAF goal: long-life structures and lower life cycle costs Real solutions to fatigue cracking & corrosion, not just replacement Reduction of inspection burden and improved fleet availability Repeatable, consistent way to decide when to retire aircraft
“Care-free” structures concept offers opportunity Truly optimized structures not min weight, but optimized for min life cycle cost Cuts structural inspection of wing by 75 - 90% and recaptures weight lost to beef-ups Retains current inspection and repair processes at lower life cycle costs
High Velocity Maintenance promises a “depot revolution” Enhanced aircraft condition awareness prior to depot cycle Better planning for more focused, shorter cycle times No surprises…No wasted motion…No waiting
Effective State Awareness crucial to accomplishing all 3
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
8
Overview
Aging aircraft in perspective
Carefree Structures
High-Velocity Maintenance
Prognosis Role as Integrator
Summary
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
9
Hybrid “Care-Free Structures” Product of Dutch/German/US research
Follows on Fiber Metal Laminates (TU Delft NL, 1980s)
Key features: Durability, damage tolerance, long inspection intervals, ease of repair, corrosion- and impact-resistant structures
Excellent Service History: 4 AC-130 flaps flown (early 1990s) 40 C-17 aft cargo doors in service (1995-present) Airbus A380 upper fuselage in service (2008)
Care-Free Concept not limited to FMLs
Put the Right Material in the Right Place!
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10
Alcoa Hybrid Wing Panel Tests (2006) Ultra-Long Life Under Severe Conditions
0
25
50
75
100
125
150
175
0 2,500 5,000 7,500 10,000 12,500 15,000 17,500 20,000 Flights
Hal
f C
rack
Len
gth
, a
[mm
]
B777 wing@ Baseline Stress
Bolt Ctr Line
Airbus 380 wing@ Baseline Stress
Transport Wing Fatigue Spectrum, saw cut with severed stringer
Baseline: mean flt = 12 ksi, max = 27.6 ksi, ground = - 6 ksi; RH > 90%
Skin side
Stringer side
Skin side
Stringer side
Desired “natural” fatigue
Early Hybrid Concept @ + 25% Stress
Al Sheets
Extruded Al Stringer
Fiber Metal Laminate
Evolved Hybrid @ +25% Stress No external crack growth
Bucci, et al, ASIP 2006
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Artificial fl
aw
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Damage Tolerance Approach Conventional Aluminum Structures
2ASIP 2006., Nov. 29, 2006
Current Practice: Inspect for Structural Safety
ResidualStrength Initial Insp.
= 1/2 life
LimitRepeat Inspections more frequent as multiple cracks occur
Ultimate
2nd Insp.= 1/4 life
1 lifeToday's Metallic
Life extension
repairs
As damage-tolerant aircraft age past original design life, inspection burden grows…
… and risk of inspection-induced damage increases
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12
Safety through inspection?
Example: bolt hole eddy current inspection of a fuel tank structures
Highly skilled technician
Hand-held eddy current probe
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
13
Example: bolt hole eddy current inspection of a fuel tank structures
Highly skilled technician Hand-held eddy current
probe, mirror, flashlight,
technical data, and NDI standards
A good NDI technician is hard to find!
Safety through inspection? Difficult
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
14
Now I think we’re prepared for the inspector to enter the wing through this spacious access hole….
Why is inspection so difficult?
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15
Safety through inspection
…rely on him to be perfect, every single time.Compliments of David CampbellOklahoma City ALC NDI Program Mgr
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16
- 1 -
Flight Cycles1X 2X 3X 4X 5X 6X
ResidualStrength
Limit LoadFail-safe req.
0
Life Extension
Inspect & Repair
"Care-free"Economic Life
1 DSG 2 DSG Current Practice: Damage Tolerance
1 DSG Proposed Care-free 2 DSG
UltimateLoad
Damage TolerantEconomic Life
Onset of widespread fatigue damage
"Care-free"1st inspection
Benefits of the Care-free design after Hinrichsen, Alcoa
Longer inspection intervals Much longer acrit, easier to find Safety, economy and availability May make enhanced state awareness easier
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17
Opportunity: Care-Free Tech Demo?AF-managed OEM effort
Program: Develop care-free form-fit replacement problem wing structure Extend life while improving availability Eliminate fatigue and corrosion, reduce inspections, cut cost Fly proof of concept with enhanced state awareness / IVSHM system?
Key Performance Parameters Triple fatigue life of current wing Eliminate PDM and all wing structural inspections in double current lifetime Visual inspections for life (no critical flaw size small enough to require NDI) Weight neutral with SOA structures
Attempt to prove maturity of prognostics in a demanding aircraft environment?
Notional Schedule: By 18 months – Design, develop test plan, build 1st article By 33 months – First lifetime of fatigue testing while transitioning to production By 33 months – Install and flight test 2nd article By 48 months – First production article in new and retrofit aircraft
PR
IOR
ITY
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
18
Overview
Aging aircraft in perspective
Carefree Structures
High-Velocity Maintenance
Prognosis Role as Integrator
Summary
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
19
High-Velocity Maintenance ALC initiative to increase aircraft availability
Reduce impact of sched maintenance on fleet availability
Raise Efficiency of Depot Maintenance Processes Low man-hour “burn rate” compared to industry
• Airlines: 500-800 man-hours/day• Depot: 145-220 hours/day
Field and Depot not synchronized• Function as two independent systems• Little communication
Aircraft condition not well known at induction• Result: Long lead times• High opportunity costs = larger than needed fleets
1000
500
0
Mx
Vel
ocit
y (h
rs/d
ay)
PDMISO ISOHSC ISO
Maintenance Cycle
“Current” State
C-130 PDM = $3.5M ea, 95/yr, 22K Hrs, 160 DaysF-15 PDM = ~$3.75M ea, 97/yrC-5 PDM = $16.3M ea, 18/yr
“To Be” State
Additional Availability
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After Dement & Keene
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HVM Vision
No Surprises…No Wasted Motion…No Waiting
Increase aircraft availability using common sense tools to
Establish a synchronized, integrated, end-to-end process
Maintenance must not impact mission requirements.
AircraftAvailability
HVM
ECSSCAMGLSC
PLM
LCSE
AAIP
HVM for PDM/ISO
WR-ALC C-130 Prototype
Optimizes the PDM process (the “how”)
Includes all supporting processes
Optim
ize the field/depot reqmts
(the “what, w
hen and where)
RCM
CBM+
MSG-3
Expands HVM to be “scalable and transportable”
Ove
rarc
hing
ent
erpr
ise
initi
ativ
es
Std Work Supply Chain Ops Lifecycle Mgmt Sourcing Tech Development
IntegrityPrograms
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
21
HVM Attributesfrom Warner Robins ALC
Current State Limited Knowledge of A/C Condition
• Two Mx systems; creates knowledge barriers
5+ Year PDM cycle (C-130)• Damage accumulates, so “must fix now” mentality
Job Shop Environment• Mechanic must fetch own tools; parts; set up
Inadequate plans – reqmts, parts, materiel, equipment• Lacks information – complete BOM, planned work, support
Stove-piped processes and execution• Lack of synchronicity leads to non-compliant work arounds
Future State Known Aircraft/End Item Condition
• Use lead time ahead of induction • Order Parts, Training, Infrastructure, Equipment, Data, etc.
Mechanic-Centric Focus (Surgeon)• Parts, tools, data, equipment pre-positioned at point of use• Maximum use of kitting
Expand Standard Work & Processes Single Maintenance Concept Integrated Planning, Decision-making, & Data Collection Equivalent to 14% more aircraft on station
Enhanced State
Awareness
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Find, then fix
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Information Enabled Planning & Execution
Spiral 3:Total Weapon System
State Awareness
Cap
abili
ty
Time
Enhanced State
Awareness
Spiral 1: Research
Supporting Key Technologies
Spiral 2:Vehicle Health Mgmt
Integrated Management System- Integrated Data from all systems- Plans/Schedules
Now
Airframe ConditionPredictive analysis- RCM, MSG-3- Dets assess condition
Airframe ConditionSHMS- On-board systems diagnostics- Corrosion sensors- 100% flight Loads dataAuto data transfer & analysis
Fully Integrated Management System- Automated Data Collection &
Distribution- Anticipatory Spares Ordering- Automated POM generation of $$
Airframe Condition- Fully Instrumented (IVHM)- Onboard Prognostics/Life Prediction
Enhanced State Awareness- Structural Integrity Prognosis
System- Active Autonomous Dialogue
with Depot
Integrated Supply Chain Management
Standard Work for ISO/PDM
Standard Work Documented for All Processes
Standard Work Documented for Integrated System
Single Maintenance Concept
Net-Centric Solution w/ Supply Base
ISO and PDM Integrated
Integrated Requirements and Funding Process
- Right maintenance accomplished when mission requirements allow
Total State Awareness determines when MX required
No surprises
Low cost per flying hr
HVM for Developmental AircraftCapability Spirals
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Total State Awareness
23
Overview
Aging aircraft in perspective
Carefree Structures
High-Velocity Maintenance
Prognosis Role as Integrator
Summary
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
24
Prognosis Role in Community Integration
How can material and structural state awareness be achieved?
What is the role of an informed maintenance community in developing the prognosis concept?
Can total vehicle state awareness be achieved at an affordable cost?
Can leadership be convinced that prognosis is a better solution?
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Desired state Damaged state Failure
After K Jata, Sept 2007
25
Prognosis as Integrator
Design
Analysis &
Development
Tests
Design
Information
(Materials
Allowables)
Full-Scale Testing
Force Management
Production, Industrialization, Safety,
Maintenance, Inspection
Sensing for State Awareness
Prediction & Prognosis
Fault Detection &
Trending
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Care-Free
Structures
Self-
heal
ing
mat
eria
ls
Failure
Progression
Failure
Analysis
26
Prognosis as Integrator
Prognosis Drivers:
Data Physics Cost Availability Capability Safety Tribal Customs
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
Prediction
CB
M+
High-V
elocity Mx
Prognosis
Dia
gnos
tics
Care-Free Structures
Aircraft Structural Integrity Program in the age of
state awareness
ASIP-SA
27
Summary
High-Velocity Maintenance Carefree structures concepts maturing
Prognosis community must integrate the “cultures” of the various “tribes” crucial to achieving USAF relevance
Possible collaboration on proposed Tech Demo will drive R&D to solve most difficult aging aircraft problems
Early transition to Tech Demo wing would challenge integrators to focus on the art of the possible.
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.